@freemo There is also the issue of early vaccination. Vaccines are much more harmful for newborns and very young children. Breastfeeding supplies all the antibodies the mother has - so if Mom has been vaccinated against polio, the newborn is protected while they are mostly breastfeeding.
When baby is getting weaned, then you look at what vaccinations might be a good idea - and prioritize, so you don't do them all at once on a very young child.